Update unless tag

[kjaymiller]

Currently not breaking anything (maybe a11y)

The condition in the 'unless' tag is malformed; it likely should be written as {% unless entry.platform == "rss" %}.

  <a {% unless entry.platform == "rss" %}rel="me" {% endunless %}href="{{ entry.user_url }}" target="_blank" title="{{ entry.title | default: entry.platform }}">

Originally posted by @Copilot in https://github.com/BlackPythonDevs/blackpythondevs.github.io/pull/717#discussion_r2169998093